KHARTOUM, Sudan — Even before Sudan’s president expelled aid groups from Darfur following an international warrant seeking his arrest, diarrhea was spreading among newcomers at one of its largest refugee camps and people waited hours in line for water.

The picture at the Zamzam Camp grew even bleaker Thursday when no aid workers showed up, leaving residents to figure out how they would get life sustaining goods from sorghum seeds to running water and tents for the influx of new refugees.

“We are very concerned,” said Ibrahim Safi, 34, one of 75,000 residents at the camp. “After God, we only have the organizations.”

U.N. Secretary-General Ban Ki-moon said Thursday that Sudan’s expulsion of 13 major aid organizations will cause “irrevocable damage” to humanitarian operations in Darfur and called on the government to urgently reconsider its decision.

Catherine Bragg, the U.N.’s deputy emergency relief coordinator, said the organizations are responsible for “at least half” of the humanitarian operations in Darfur and are vital partners for U.N. agencies in delivering food, providing health care, water, education and other services.

“With the loss of these NGOs, 1.1 million people will be without food aid, 1.1 million will be without health care, and over 1 million will be without potable water,” she said.

In his first comments since the International Criminal Court issued a warrant Wednesday charging him with war crimes in Darfur, Sudanese President Omar al-Bashir defiantly accused the tribunal, the U.N. and the aid organizations of being part of a new “colonialism” that wants to destabilize his country.

Al-Bashir said the aid organizations were trying to disrupt peace efforts in Darfur, profiting from the conflict and interfering with foreign investment.

The head of the government agency that oversees Sudan’s humanitarian affairs, Hasabo Abdel Rahman, also directly accused the expelled aid groups of cooperating with the ICC and giving the court “false” testimony.

The nongovernmental aid groups, which include CARE International, Oxfam GB and Mercy Corps, have denied any involvement with the ICC. But experts had warned of possible repercussions against the groups if the arrest warrant was ordered.

Eric Reeves, a Sudan expert and professor at Smith College in Massachusetts, said the decision to expel so many aid groups was “without precedent” — but not surprising. Harassment of aid groups and denial of access to Darfur were common practices by the Khartoum government before the decision, he said.